Bull C M, Burzacott D
Flinders University, School of Biological Sciences, GPO Box 2100, Adelaide, South Australia 5001, Australia.
Mol Ecol. 2001 Mar;10(3):639-48. doi: 10.1046/j.1365-294x.2001.01214.x.
Two tick species Aponomma hydrosauri and Amblyomma limbatum that infest large reptiles have an abrupt parapatric boundary near Mt Mary in South Australia. A previous model has suggested that the boundary is maintained at population density troughs resulting from habitat heterogeneity along a gradual environmental gradient. This paper describes the dynamics of the boundary on three transects over 17 years, 1982-98. Over the last seven years of that period there has been a significant increase in rainfall. At the same time, the boundary position has moved 1-2 km on the transects, with the more mesic adapted Ap. hydrosauri advancing into the distribution of the more xeric adapted Amb. limbatum. Also over the same time the density of ticks on lizards in regions flanking the boundary zone has increased for Ap. hydrosauri and decreased for Amb. limbatum. These results suggest that the environmental gradient has been altered, perhaps by increased rainfall, to favour Ap. hydrosauri, which has been able to colonize more successfully across the density troughs and extend its distribution.
两种寄生于大型爬行动物的蜱虫物种——水龙硬蜱（Aponomma hydrosauri）和缘纹硬蜱（Amblyomma limbatum），在南澳大利亚的玛丽山附近存在一个明显的邻域分布边界。先前的一个模型表明，该边界维持在因沿渐变环境梯度的栖息地异质性导致的种群密度低谷处。本文描述了1982年至1998年期间，在三条样带上该边界17年的动态变化。在该时期的最后七年里，降雨量显著增加。与此同时，样带上的边界位置移动了1 - 2公里，适应性更强的水龙硬蜱向适应性更强的缘纹硬蜱分布区域推进。同样在同一时期，边界区域两侧蜥蜴身上的蜱虫密度，水龙硬蜱增加了，缘纹硬蜱减少了。这些结果表明，环境梯度可能因降雨量增加而发生了改变，从而有利于水龙硬蜱，使其能够更成功地跨越密度低谷进行定殖并扩大其分布范围。
